Split Pairs

One of the most common problems encountered when installing Ethernet extenders are split pairs.  All Netsys Ethernet extenders that run over network-grade cable or existing phone wiring require a twisted pair to carry the signal.  Like it sounds, a twisted pair is two wires twisted together, and the majority cables have multiple twisted pairs in them.  Twisting the wires together helps to eliminate electrical noise entering into and leaving the cable and helps minimize cross-talk (signals leaking between wires in a cable).  A split pair is when one wire from one pair gets swapped with another wire from a second pair at both ends of the cable.  A split pair negates the effect of having a twisted pair and renders the cable unsuitable for carrying broadband data.  The symptoms of a split pair can vary depending on the length of the line with the split pair and the quality of the cable, ranging from the Ethernet extenders linking but passing data very slowly to unstable links to no link at all.  See the diagram below for an example of a split pair.

Because most cables have multiple twisted pairs, split pairs are a common error that can be easy to make, but more difficult to detect due to the fact that continuity, resistance, and insulation tests will not detect a split pair.  The easiest way to check for split pairs is to do a visual inspection of the terminations along the length of the cable.  There are also several testers available that can check for split pairs, although they are specialized and can be expensive.  If you are unable to get your Ethernet extenders to link up and pass data normally when installing them, try linking them up over a short run of cable in a testing environment to make sure they are working first, and then check your terminations to make sure you have the correct two wires (the two that are twisted together) punched down on the correct pins throughout the length of the line.  Remember, just because a pair has continuity does not mean it is wired correctly!

As always, if you have any questions regarding this topic or any other support questions, feel free to email us at support@netsys-america.com and our support team will be happy to help you out.  Thanks for checking out Netsys Direct for your networking needs!